m‐Metallaphenol: Synthesis and Reactivity Studies

Abstract

Treatment of the osmium complex [Os{CHC-(PPh3 )CH(OH)-η(2) -C≡CH}(PPh3 )2 (NCS)2 ] (1) with excess triethylamine produces the first m-metallaphenol complex [Os{CHC(PPh3 )CHC(OH)CH}(PPh3 )2 (NCS)2 ] (2). The NMR spectroscopic and structural data as well as the nucleus-independent chemical-shift (NICS) values suggest that osmaphenol 2 has aromatic character. The reactivity studies demonstrate that 2 can react with different isocyanates to form the annulation reaction products [Os{CHC(PPh3 )CHC(OCONR)C}(PPh3 )2 (NCS)2 ] (R=Ph (3), iPr (7), Bn (8)) via the carbamate intermediates [Os{CHC(PPh3 )CHC(O-CONHR)CH}(PPh3 )2 (NCS)2 ] (R=Ph (4), iPr (5), Bn (6)). In addition, the similar annulation reactions can be extended to other unsaturated compounds containing N-C multiple bonds, for example, isothiocyanates, pyridine, and sodium thiocyanate, which can produce the corresponding fused osmabenzene complexes. In contrast, the reactions of 2 with common electrophiles, such as NOBF4 , NO2 BF4 , N-bromosuccinimide, and N-chlorosuccinimide only led to the decomposition of the metallaphenol ring. The experimental results suggest that 2 is very electrophilic and readily reacts with nucleophiles, which is mainly due to the metal center and the strong electron-withdrawing phosphonium group.

Access to Metal‐Bridged Osmathiazine Derivatives by a Formal [4+2] Cyclization

“…[4e] Various metallacycles that contain one or two main-group heteroatoms have been isolated,s uch as metallapyridines, [6k, 14] metallapyridynes, [6k] metallathiobenzenes, [15] metallabenzothiophenes, [16] metallabenzofurans, [17] metallabenzothiazoles, [6j, 18] metallabenzoxazoles, [18] metallabenzoxathialoes, [19] and metallabenzoxolones. [20] This strategy significantly enriches the structurala nd compositional varieties of metallacycles.…”

Phosphonium salts and P-ylides

“…Zhang, Xia and co-workers prepared and characterised an osmaphenol complex (in which osmium is part of the aromatic ring) bearing a triphenylphosphonium group. 13 The use of phosphonium groups in the preparation of this class of organometallic compound is very common as observed in a recent review by Cao et al 14 Dimé et al reported that controlled potential electrolysis of a triarylmesosubstituted Ni(II) porphyrin in the presence of triphenylphosphine as a nucleophile allowed the electrochemical synthesis of the corresponding phosphonium derivative. 15 Polymeric organometallic materials were also described.…”

Reactions of Metal–Carbon Bonds within Six‐Membered Metallaaromatic Rings

“…Hydroxyl group substituted osmabenzene, that is, m ‐osmaphenol can also perform similar S N Ar reactions. By treatment of different isocyanates with m ‐osmaphenol, a series of osmabenzenes with urethane linkages could be generated . The following intramolecular S N Ar reaction by urethane linkages in the presence of bases afforded a series of annulation products.…”